Intermolecular forces problems

Why the boiling point of HBr will smaller than the Cl2 ?
Since the relative molecular mass of HBr is bigger than Cl2 , so the temporary dipole induced dipole forces should be bigger . Thus , the boiling point of HBr should be bigger .

This is not true... the molecular mass that relates to London forces (which is a relatively weak intermolecular force) does not have such an impact in this case. Think about the electronegativity difference between H and Br. Also, think about whether or not there is hydrogen bonding (a relatively strong intermolecular force) between H and Br. You cannot deduce relative boiling points simply looking at one aspect of the problem.